TABLE 4.

Library 2 amino acid representation

Amino acid(s)	Frequencya		Odds ratiob	P valuec
	Selected [PSI+] library	Unselected naive library
Tryptophan (W)	0.042	0.009	4.71	0.013
Phenylalanine (F)	0.064	0.021	3.16	0.011
Asparagine (N)	0.068	0.040	1.77	0.14
Methionine (M)	0.030	0.021	1.43	0.60
Glycine (G)	0.057	0.046	1.26	0.58
Isoleucine (I)	0.038	0.030	1.25	0.65
Cysteine (C)	0.015	0.012	1.25	1.00
Histidine (H)	0.080	0.070	1.15	0.75
Valine (V)	0.038	0.037	1.04	1.00
Glutamic acid (E)	0.023	0.024	0.93	1.00
Serine (S)	0.110	0.119	0.91	0.80
Threonine (T)	0.087	0.095	0.91	0.78
Alanine (A)	0.057	0.064	0.88	0.73
Leucine (L)	0.045	0.052	0.87	0.85
Glutamine (Q)	0.030	0.037	0.82	0.82
Tyrosine (Y)	0.049	0.064	0.76	0.48
Proline (P)	0.072	0.095	0.74	0.37
Aspartic acid (D)	0.045	0.067	0.66	0.29
Arginine (R)	0.045	0.076	0.58	0.17
Lysine (K)	0.004	0.021	0.17	0.081
Groups
Aromatic (FWY)	0.155	0.095	1.76	0.031
Hydrophobic (FILMV)	0.216	0.162	1.43	0.11
Charged (DEKR)	0.117	0.189	0.57	0.023
Positive (KR)	0.049	0.098	0.48	0.029
Negative (DE)	0.068	0.091	0.73	0.36
Polar (NQHST)	0.375	0.360	1.07	0.73
Q/N	0.098	0.076	1.32	0.38

^aThe [PSI⁺] value represents the frequency of occurrence of the amino acid among the prion-forming isolates; the naive value represents the frequency of occurrence of the amino acid among the unselected clones.

^bOdds ratios were calculated using equation 2.

^cP value is based on the 2-tailed Fisher exact probability test.